Fire Fighters: The arc of safety bends toward AFCIs

Once a bedroom-only requirement, arc-fault 
circuit interrupters (AFCIs)­—either as breakers or receptacles—today are required in almost all areas of the home. The 2014 edition of the National 
Electrical Code (NEC), in effect in 27 states as of March 2016, has added kitchens, laundry areas and dormitory rooms to the list of living spaces in which such protection is necessary. Now, more than ever, electrical contractors (ECs) need to educate themselves on where AFCI protection is required and how to use the devices’ increasingly sophisticated onboard diagnostics to track down fault locations when trip events occur.


A bedroom-circuit requirement took effect in 2002, but the 1999 NEC introduced AFCIs. The devices were developed to reduce the number of home fires related to electrical-system malfunctions. As recently as 2011, an estimated 47,700 home fires were linked to electrical problems, according to the National Fire Protection Association (NFPA). Initially, AFCIs were designed only to detect parallel arcs—the type that might occur when a nail or staple damages the insulation separating electrical wires from each other. The 2005 NEC initiated the move to combination-type AFCIs that also activate in the case of series arcs, which might occur with a loose connection or damaged insulation within a single wire.


Combination-type AFCIs add a layer of intelligence to the operation of the basic, run-of-the-mill circuit breaker. Their internal circuitry monitors waveform characteristics and heat to detect potential problems.


“On top of having the thermomagnetic caps, it looks at the sine waves that come off the power line,” said Ashley Bryant, product manager with Siemens. 


Though manufacturers might use slightly different approaches, each has, in general, developed algorithms that enable the breakers to ignore patterns outside normal ranges that are the harmless byproducts of electronics, appliances and other common household loads.


Constant evolution to meet new loads


Over the years, AFCIs have had their detractors, including opponents who argue the devices can trip in the absence of a true fault, called “nuisance” tripping. Manufacturers admit that the technology had issues, especially in its early days, in part because every home’s electrical load is unique, and developers weren’t able to test every possible combination of loads and breakers.


“When you design any product, you design it to meet certain standards,” Bryant said. 


In the case of AFCIs, this is Underwriters Laboratories (UL) Standard 1699, Standard for Arc-Fault Circuit Interrupters.


“You do as much testing as you possibly can, but as soon as you put it out in the field, there are going to be surprises,” she said.


Among those early surprises were discoveries of radio frequency interference that mimicked the appearance of an arc fault, along with appliances and other connected loads that regularly operated outside the parameters of their own defined UL standards. Bryant said AFCI manufacturers now regularly re-evaluate their devices’ performance against new-to-market electrical and electronic products.


“We’ve done is we’ve purchased these devices,” she said. “If we deem them safe, then we’re able to ignore some of those algorithms. Ultimately, this is a safety device. If it’s tripping and your power’s going out, it’s going to drive you crazy. Our job is to try to make it work to the best of its ability in the field. It’s a fine line.”


Siemens isn’t alone in its efforts to ensure AFCI breakers and receptacles are compatible with a broad range of connected loads, from appliances to home electronics. In fact, all of the major circuit-breaker manufacturers—which, in the United States include Eaton, GE, Schneider Electric and Siemens—have programs to ensure their products keep up with the ever-evolving consumer marketplace.


“We’ve entered into partnerships with appliance manufacturers, device manufacturers and lighting manufacturers,” said Lanson Relyea, product line manager for miniature breakers at Eaton. “They recognize the need to be compatible, as we do.”


This evaluation also includes investigations in customer homes, in which tripping causes can’t be identified.


“We want to capture as much data from that house to understand how the products interact in the field,” Relyea said.


Tracking faults to their source


Alan Manche, vice president of external affairs for Schneider Electric, has experienced some of this frustration firsthand. He has learned from experience that what may initially be seen as nuisance-tripping more often is the result of real electrical problems going undetected. 


[SB]In one instance, the problem was a loose connection in a receptacle that allowed conductors to jostle against each other whenever his young children were playing nearby. In a second case, he found the cause of frequent tripping in a pair of can-style lighting fixtures so poorly installed that wiring insulation had been damaged inside the cans. In both cases, what he initially thought was just a nuisance was actually a potential fire waiting to ignite.


“The AFCI takes a hit, when, in fact, it’s doing its job,” Manche said. “Hunt a little harder, and let us help you hunt a little harder, and I think you’ll uncover some issues that are there.”


That hunting process has become easier over the last few years as manufacturers have incorporated some form of onboard diagnostic tools to help electrical contractors track down what kind of fault they might be dealing with, along with where in the circuit it might be located. Also, manufacturers have technical support available by phone (see sidebar).


“I really encourage them, if they have an issue, to get in contact with the manufacturer,” Relyea said. “That’s the only way we can get better with the product.”


Several approaches to the same end


Knowing where AFCI protection is required, and what kind of protection is allowed, also can be a bit confusing. Certainly, the first question ECs need to answer is which NEC version (if any) is in effect in their state and how the authority having jurisdiction (AHJ) in their municipality or county interprets NEC requirements.


With an understanding of local requirements as a foundation, electrical contractors then face the task of determining the best approach to AFCI protection for a specific project. At a high level, the most likely options (again, based on local AHJ approval) include the following:


• A combination-type AFCI breaker


• A combination-type AFCI breaker that also offers ground-fault circuit interrupter (GFCI) protection (called a “dual-function” AFCI/GFCI breaker)


• A combination-type AFCI (or dual-function) receptacle installed as the first electrical outlet in a circuit. This option requires the home-run wiring that leads back to the panel to be installed in metal conduit or in metal or nonmetallic conduit that is encased in at least 2 inches of concrete.


• Some combination of a branch-feeder-type AFCI (one that only protects against parallel arc faults) along with an AFCI receptacle at the first outlet.


The argument in favor of using AFCI receptacles instead of, or in addition to, some variety of AFCI breaker lies largely in the accessibility of the reset function. An AFCI receptacle has a reset button right on its face, at the point of use, while a tripped breaker will require a visit to the panel for resetting and troubleshooting. While centralizing protection in a single device, the breaker can ease troubleshooting. Manche said AFCI receptacles offer advantages for specific installations.


“I think if you’re trying to put all the [protective] pieces in one place, being able to go to that one spot is fairly simple for the contractor,” he said. “You know exactly which breaker has tripped, and it has a memory.”


While few ECs are likely to go through the added expense of adding conduit to a project where it’s otherwise not called for, AFCI receptacles might make sense in projects such as large dormitories or high-rise residential structures where conduit is already a requirement.


“You probably don’t typically see a contractor putting a conduit in just to get a receptacle, but there are markets where you have conduit, and it’s simply an option at that point,” Manche said.


Safety is no nuisance


The days of debating AFCI devices have passed. The added safety these breakers and receptacles provide in the face of potential electrical fire hazards is simply too great to ignore. As manufacturers have fine-tuned the algorithms their products use to ignore false-positive sine wave patterns, a thorough investigation much more often finds what ECs used to term “nuisance tripping” to be a potentially dangerous wiring condition.


“I don’t like to call it nuisance-tripping. I like to call it a safety alert. Nine out of 10 times, there’s an issue. When that breaker is tripping, there’s usually some type of event going on.”


About the Author

Chuck Ross

Freelance Writer

Chuck Ross has covered building and energy technologies and electric-utility business issues for a range of industry publications and websites for more than 25 years. Contact him at chuck@chuck-ross.com.

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